Coronary heart disease continues to be the leading cause of death in the United States, despite risk factor reduction and technological advances in treatment options. Prospective studies implicate chronic anxiety as an independent risk factor for fatal coronary heart disease. In particular, anxiety increases the risk of sudden cardiac death substantially. The primary objective of the proposed research is to examine the role of reduced vagal control of heart rate in the increased risk of cardiac mortality associated with anxiety in a population with established coronary artery disease (CAD). A second objective is to determine whether the effects of anxiety are independent of the effects of depression. Nine hundred and fifty CAD patients will be recruited for this study from patients hospitalized for elective cardiac catheterization. Anxiety will be measured by the Hospital Anxiety Scale, the Spielberger Trait Anxiety Inventory, and the Crown-Crisp Phobic Anxiety Scale. Symptoms of depression will be measured by the Montgomery-Asberg Depression Rating Scale, the Hospital Depression Scale, and the Beck Depression Inventory. Vagal control of heart rate will be determined using power spectral analysis to measure two indices of vagal control: baroreceptor-mediated vagal reflex cardiac control, and respiratory sinus arrhythmia. Patients will be followed at 6 months, l year, 2 years, and 3 years postcatheterization, and cardiac mortality data will be obtained, including non-sudden and sudden cardiac death. The data generated by this study will be used to examine the involvement of impaired vagal cardiac control in the risk of fatal coronary heart disease and sudden cardiac death associated with anxiety. Specifically, the proposed study will examine: (1) the relationship between anxiety and cardiac mortality; (2) the relationship between anxiety and vagal control; (3) the role played by reduced vagal control in mediating anxiety-related risk; and (4) the relationship between depression, vagal control and cardiac risk. Findings of a relationship between anxiety, reduced vagal control and sudden cardiac death would suggest the potential importance of early intervention in cardiac patients with anxiety disorders and would underscore the benefit of aggressive monitoring of arrhythmias in this population, which may ultimately translate to reduced mortality rates.